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Modern birds may have evolved before the mass extinction of the dinosaurs some 65 million years ago, the event many believe shaped animal diversity today, a study suggests.

New analysis of a bird fossil Vegavis iaai found in Antarctica in the 1990s says it is a relative of modern ducks and geese, suggesting the evolution of modern birds was well under way during the Cretaceous.

The bird lived some 70 million years ago and was a contemporary of the dinosaurs.

Scientists originally thought it was part of the lineage that includes today's ducks and geese, but was not itself a direct relative of this group.

This latest analysis suggests otherwise, fuelling the debate about when modern birds emerged.

Adding to the debate

Ornithologists are still debating whether modern bird groups existed in the Cretaceous or if they evolved in a 'Big Bang' in the Tertiary about 65 million years ago, after the dinosaurs became extinct.

Big Bang proponents say this could happen mainly because the surviving species from the mass extinction could exploit habitat niches vacated by the dinosaurs.

They say the then few lineages of modern birds underwent a massive radiation and diversification within a few million years after the Cretaceous, giving rise to most of the modern groups.

According to their interpretation of the avian Cretaceous fossil record, very few specimens can be allocated to modern lineages, proof these lineages did not exist at this time.

But another interpretation places a number of the fossils within modern lineages.

In this latest analysis the scientists describe how they compared morphological characters (the bumps and the grooves) preserved in the fossil with those found in other fossils and in the skeletons of modern birds.

They then analysed the data to determine the genealogical position of this fossil bird relative to other fossil and living birds.

From this, the scientists conclude V. iaai is in fact a direct ancestor of living waterfowl.

Walter Boles, an ornithologist at the Australian Museum in Sydney, says that because Australia was connected with Antarctica at this time, the findings imply that modern bird groups were also present in Australia in the Cretaceous.